SparkFun Forums

[zokko]

Hi,

I have now reached the point of giving up and placing my em406A module on that shelf in the garage where it only gathers dust. I'm so frustrated ( yep, I'm at that point ) I just want to give up and open a beer.

But perhaps, someone out there can help me!!! I'm using the DiosPro Pic from www.KronosRobotics.com. I originally had every running at 5Volts but was not getting any output from the EM406A, Then I noticed that a lower voltage ( 3.3V ) actually allows me to see some NEMA strings but they are garballed. I check the baud rate like everynight so that isnt the issue.

BTW, I've hooked the EM406A to the eval board and it works great, so the unit is functioning properly. There seems to be some volatge issue, but I dont have a clue. For hookup, I've only connected the Vcc, Grnds and TX wires. The RX and PPS wires are not connected.

This is just madness! ARRRGGGGHHHHH!!!!! Someone please help!

[zokko]

Oh one more thing, I've ran across some statements like

doing "logic level shifting if your uProcessor is running at 5V." What the heck does this mean?

thanks again!!!!

[RealMcG]

Hi Zokko.

The most common cause of problems with these connections is just inverted polarity on the serial line, i.e. + is connectet to - and vice versa.

Here, you also mention Logic Level Shifting. This means, that if the receiver of the data string is expecting the logical high to be in the 5V region, the bit 1, the voltage will be for example somewhere wetween 4 and 5.5 V, while logical low wil be between -.1 and 3.7. Voltages in the region between 3.7 and 4 is then generally not allowed, and the result CAN be garbage, but it CAN also work.

If the sender is of the 3.3V logic high type, the logical 1 wil be somewhere around 2.7 to 3.7V, not sufficient to be in the above specified receivers alloved input voltage region, and can give garbage results.

By using a Logical Level Shifter, a 3.3V sender can pass its output into this logical level shifter, and provide valid 5V logical signals from the output of this Logical Level Shifter.

Hope this helps you futher!